disaster recovery validation

Disaster recovery validation on Windows systems involves ensuring that backup images can be successfully mounted and restored after security updates. A recent thread highlights that Microsoft's KB5083769 update, released April 14, 2026, blocks the psmounterex.sys driver, breaking disk-image mounting in tools like Macrium Reflect, Acronis Cyber Protect Cloud, UrBackup Server, and NinjaOne Backup. Microsoft considers this an intentional enforcement of its vulnerable driver blocklist due to a known privilege-escalation flaw, not a patch defect. This means administrators must validate recovery workflows after updates and rely on backup vendors for fixes, as Microsoft will not roll back the change. The risk affects any organization depending on these tools for disaster recovery.